The formation of a high-resolution three-dimensional image of a scene using a two-dimensional image sensor remains a complicated operation in modern optics. Ideally, a camera could reconstruct an image of the scene over the entire range of object distances without requiring scanning of the camera focus of the range. Preferably, the three-dimensional image could be acquired in a single snapshot. Unfortunately, modern cameras are still characterized by the need focus on only a single plane of the object and light from other ranges of the scene serve only to degrade the image formed by the camera rather than contribute useful image data.
Various volume-imaging cameras for reconstructing three-dimensional images using multiplexed measurements have been presented in the prior art. Typically, these approaches apply digital processing to invert multiplexed image data and estimate the three-dimensional object. Recently, volume imagers have evolved from analog two-dimensional slice selection to using computation to estimate a complete volume image.
Unfortunately, the strategies employed in modern volume imaging, such as focal scanning, radiance sampling, and wavefront coding universally trade reductions in transverse or temporal resolution for improved longitudinal resolution.
Scanning the focus of a lens through a range of depths-of-field (i.e., focal scanning) is one method for volume imaging. The simplest approach for focal scanning is based on the use autofocus as applied to conventional digital cameras. In such an approach, a sharpness metric is optimized at a plurality of depths-of-field to form a series of two-dimensional images. These two-dimensional images are then combined to realize a three-dimensional image.
Unfortunately, sequential acquisition of any reasonable number of two-dimensional images is inefficient and reduces the effective frame acquisition rate.
Radiance sampling uses a light-field camera that is based on a microlens array to attempt to characterize the radiance at each point in the three-dimensional image volume of the camera. Although showing some promise as volume-imaging technique, radiance-sampling cameras are likely to suffer from modal error. Further, lateral image resolution is limited by the aperture diameter of the lenslets used to form the camera.
Wavefront coding is a form of computational photography that uses a cubic-phase modulating element in conjunction with deconvolution to extend the depth of field of a digital imaging system such as a video camera. Unfortunately, wavefront coding reduces the modulation transfer function at all focal ranges of the imaging system, which degrades transverse image resolution.
A means for developing a high-resolution three-dimensional rendering of a three-dimensional scene using a two-dimensional image sensor that overcomes some of the disadvantages of prior-art imaging systems would be a significant advance in the state of the art.